Contract-based Service Aggregation

We present a methodology for the automated selection and aggregation of (Web) services with the purpose of satisfying client queries. A key ingredient of our approach is the notion of service contract, which consists of signature (WSDL), ontology information (OWL), and behaviour specification (YAWL). The methodology inputs a registry of service contracts and a client service contract, and it automatically generates aggregated contracts that fulfil the request. By trace inspection we first individuate candidate sets of contracts that could satisfy the query collectively. For each candidate set, we generate the contract of the aggregate by suitably building its control- and data-flow, and we verify whether it actually complies with the request.